render_layer.cpp

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        // Our scrollbar widgets paint exactly when we tell them to, so that they work properly with
        // z-index.  We paint after we painted the background/border, so that the scrollbars will
        // sit above the background/border.
        paintScrollbars(p, damageRect);
#endif
        // Restore the clip.
        restoreClip(p, paintDirtyRect, damageRect);
    }

    // Now walk the sorted list of children with negative z-indices.
    if (m_negZOrderList) {
        uint count = m_negZOrderList->count();
        for (uint i = 0; i < count; i++) {
            RenderLayer* child = m_negZOrderList->at(i);
            child->paintLayer(rootLayer, p, paintDirtyRect, haveTransparency, selectionOnly, paintingRoot);
        }
    }

    // Now establish the appropriate clip and paint our child RenderObjects.
    if (shouldPaint && !clipRectToApply.isEmpty()) {
#if APPLE_CHANGES
        // Begin transparency layers lazily now that we know we have to paint something.
        if (haveTransparency)
            beginTransparencyLayers(p);
#endif

        // Set up the clip used when painting our children.
        setClip(p, paintDirtyRect, clipRectToApply);

        int tx = x - renderer()->xPos();
        int ty = y - renderer()->yPos() + renderer()->borderTopExtra();
        RenderObject::PaintInfo info(p, clipRectToApply,
                                     selectionOnly ? PaintActionSelection : PaintActionChildBlockBackgrounds,
                                     paintingRootForRenderer);
        renderer()->paint(info, tx, ty);
        if (!selectionOnly) {
            info.phase = PaintActionFloat;
            renderer()->paint(info, tx, ty);
            info.phase = PaintActionForeground;
            renderer()->paint(info, tx, ty);
            info.phase = PaintActionOutline;
            renderer()->paint(info, tx, ty);
        }

        // Now restore our clip.
        restoreClip(p, paintDirtyRect, clipRectToApply);
    }

    // Now walk the sorted list of children with positive z-indices.
    if (m_posZOrderList) {
        uint count = m_posZOrderList->count();
        for (uint i = 0; i < count; i++) {
            RenderLayer* child = m_posZOrderList->at(i);
            child->paintLayer(rootLayer, p, paintDirtyRect, haveTransparency, selectionOnly, paintingRoot);
        }
    }

#if APPLE_CHANGES
    // End our transparency layer
    if (isTransparent() && m_usedTransparency) {
        p->endTransparencyLayer();
        m_usedTransparency = false;
    }
#endif
}

bool
RenderLayer::hitTest(RenderObject::NodeInfo& info, int x, int y)
{
#if APPLE_CHANGES
    // Clear our our scrollbar variable
    RenderLayer::gScrollBar = 0;
#endif

    renderer()->document()->updateLayout();

    QRect damageRect(m_x, m_y, width(), height());
    RenderLayer* insideLayer = hitTestLayer(this, info, x, y, damageRect);

    // Now determine if the result is inside an anchor; make sure an image map wins if
    // it already set URLElement and only use the innermost.
    NodeImpl* node = info.innerNode();
    while (node) {
        if (node->hasAnchor() && !info.URLElement())
            info.setURLElement(node);
        node = node->parentNode();
    }

    // Next set up the correct :hover/:active state along the new chain.
    updateHoverActiveState(info);

    // Now return whether we were inside this layer (this will always be true for the root
    // layer).
    return insideLayer;
}

RenderLayer*
RenderLayer::hitTestLayer(RenderLayer* rootLayer, RenderObject::NodeInfo& info,
                          int xMousePos, int yMousePos, const QRect& hitTestRect)
{
    // Calculate the clip rects we should use.
    QRect layerBounds, bgRect, fgRect;
    calculateRects(rootLayer, hitTestRect, layerBounds, bgRect, fgRect);

    // Ensure our z-order lists are up-to-date.
    updateZOrderLists();

    // This variable tracks which layer the mouse ends up being inside.  The minute we find an insideLayer,
    // we are done and can return it.
    RenderLayer* insideLayer = 0;

    // Begin by walking our list of positive layers from highest z-index down to the lowest
    // z-index.
    if (m_posZOrderList) {
        uint count = m_posZOrderList->count();
        for (int i = count-1; i >= 0; i--) {
            RenderLayer* child = m_posZOrderList->at(i);
            insideLayer = child->hitTestLayer(rootLayer, info, xMousePos, yMousePos, hitTestRect);
            if (insideLayer)
                return insideLayer;
        }
    }

    // Next we want to see if the mouse pos is inside the child RenderObjects of the layer.
    if (containsPoint(xMousePos, yMousePos, fgRect) &&
        renderer()->hitTest(info, xMousePos, yMousePos,
                            layerBounds.x() - renderer()->xPos(),
                            layerBounds.y() - renderer()->yPos() + m_object->borderTopExtra(), HitTestDescendants)) {
        // for positioned generated content, we might still not have a
        // node by the time we get to the layer level, since none of
        // the content in the layer has an element. So just walk up
        // the tree.
        if (!info.innerNode()) {
            for (RenderObject *r = renderer(); r != NULL; r = r->parent()) {
                if (r->element()) {
                    info.setInnerNode(r->element());
                    break;
                }
            }
        }

        if (!info.innerNonSharedNode()) {
             for (RenderObject *r = renderer(); r != NULL; r = r->parent()) {
                 if (r->element()) {
                     info.setInnerNonSharedNode(r->element());
                     break;
                 }
             }
        }
        return this;
    }

    // Now check our negative z-index children.
    if (m_negZOrderList) {
        uint count = m_negZOrderList->count();
        for (int i = count-1; i >= 0; i--) {
            RenderLayer* child = m_negZOrderList->at(i);
            insideLayer = child->hitTestLayer(rootLayer, info, xMousePos, yMousePos, hitTestRect);
            if (insideLayer)
                return insideLayer;
        }
    }

    // Next we want to see if the mouse pos is inside this layer but not any of its children.
    if (containsPoint(xMousePos, yMousePos, bgRect) &&
        renderer()->hitTest(info, xMousePos, yMousePos,
                            layerBounds.x() - renderer()->xPos(),
                            layerBounds.y() - renderer()->yPos() + m_object->borderTopExtra(),
                            HitTestSelf))
        return this;

    // No luck.
    return 0;
}

void RenderLayer::calculateClipRects(const RenderLayer* rootLayer)
{
    if (m_clipRects)
        return; // We have the correct cached value.

    if (!parent()) {
        // The root layer's clip rect is always just its dimensions.
        m_clipRects = new (m_object->renderArena()) ClipRects(QRect(0,0,width(),height()));
        m_clipRects->ref();
        return;
    }

    // Ensure that our parent's clip has been calculated so that we can examine the values.
    parent()->calculateClipRects(rootLayer);

    // Set up our three rects to initially match the parent rects.
    QRect posClipRect(parent()->clipRects()->posClipRect());
    QRect overflowClipRect(parent()->clipRects()->overflowClipRect());
    QRect fixedClipRect(parent()->clipRects()->fixedClipRect());

    // A fixed object is essentially the root of its containing block hierarchy, so when
    // we encounter such an object, we reset our clip rects to the fixedClipRect.
    if (m_object->style()->position() == FIXED) {
        posClipRect = fixedClipRect;
        overflowClipRect = fixedClipRect;
    }
    else if (m_object->style()->position() == RELATIVE)
        posClipRect = overflowClipRect;
    else if (m_object->style()->position() == ABSOLUTE)
        overflowClipRect = posClipRect;

    // Update the clip rects that will be passed to child layers.
    if (m_object->hasOverflowClip() || m_object->hasClip()) {
        // This layer establishes a clip of some kind.
        int x = 0;
        int y = 0;
        convertToLayerCoords(rootLayer, x, y);

        if (m_object->hasOverflowClip()) {
            QRect newOverflowClip = m_object->getOverflowClipRect(x,y);
            overflowClipRect  = newOverflowClip.intersect(overflowClipRect);
            if (m_object->isPositioned() || m_object->isRelPositioned())
                posClipRect = newOverflowClip.intersect(posClipRect);
        }
        if (m_object->hasClip()) {
            QRect newPosClip = m_object->getClipRect(x,y);
            posClipRect = posClipRect.intersect(newPosClip);
            overflowClipRect = overflowClipRect.intersect(newPosClip);
            fixedClipRect = fixedClipRect.intersect(newPosClip);
        }
    }

    // If our clip rects match our parent's clip, then we can just share its data structure and
    // ref count.
    if (posClipRect == parent()->clipRects()->posClipRect() &&
        overflowClipRect == parent()->clipRects()->overflowClipRect() &&
        fixedClipRect == parent()->clipRects()->fixedClipRect())
        m_clipRects = parent()->clipRects();
    else
        m_clipRects = new (m_object->renderArena()) ClipRects(overflowClipRect, fixedClipRect, posClipRect);
    m_clipRects->ref();
}

void RenderLayer::calculateRects(const RenderLayer* rootLayer, const QRect& paintDirtyRect, QRect& layerBounds,
                                 QRect& backgroundRect, QRect& foregroundRect)
{
    if (parent()) {
        parent()->calculateClipRects(rootLayer);
        backgroundRect = m_object->style()->position() == FIXED ? parent()->clipRects()->fixedClipRect() :
                         (m_object->isPositioned() ? parent()->clipRects()->posClipRect() :
                                                     parent()->clipRects()->overflowClipRect());
        backgroundRect = backgroundRect.intersect(paintDirtyRect);
    } else
        backgroundRect = paintDirtyRect;
    foregroundRect = backgroundRect;

    int x = 0;
    int y = 0;
    convertToLayerCoords(rootLayer, x, y);
    layerBounds = QRect(x,y,width(),height());

    // Update the clip rects that will be passed to child layers.
    if (m_object->hasOverflowClip() || m_object->hasClip()) {
        // This layer establishes a clip of some kind.
        if (m_object->hasOverflowClip())
            foregroundRect = foregroundRect.intersect(m_object->getOverflowClipRect(x,y));
        if (m_object->hasClip()) {
            // Clip applies to *us* as well, so go ahead and update the damageRect.
            QRect newPosClip = m_object->getClipRect(x,y);
            backgroundRect = backgroundRect.intersect(newPosClip);
            foregroundRect = foregroundRect.intersect(newPosClip);
        }

        // If we establish a clip at all, then go ahead and make sure our background
        // rect is intersected with our layer's bounds.
        backgroundRect = backgroundRect.intersect(layerBounds);
    }
}

static bool mustExamineRenderer(RenderObject* renderer)
{
    if (renderer->isCanvas() || renderer->isRoot() || renderer->isInlineFlow())
        return true;

    QRect bbox = renderer->borderBox();
    QRect overflowRect = renderer->overflowRect(false);
    if (bbox != overflowRect)
        return true;
    QRect floatRect = renderer->floatRect();
    if (bbox != floatRect)
        return true;

    return false;
}

bool RenderLayer::intersectsDamageRect(const QRect& layerBounds, const QRect& damageRect) const
{
    return mustExamineRenderer(renderer()) || layerBounds.intersects(damageRect);
}

bool RenderLayer::containsPoint(int x, int y, const QRect& damageRect) const
{
    return mustExamineRenderer(renderer()) || damageRect.contains(x, y);
}

void RenderLayer::clearClipRects()
{
    if (!m_clipRects)
        return;

    clearClipRect();

    for (RenderLayer* l = firstChild(); l; l = l->nextSibling())
        l->clearClipRects();
}

void RenderLayer::clearClipRect()
{
    if (m_clipRects) {
        m_clipRects->deref(m_object->renderArena());
        m_clipRects = 0;
    }
}

// This code has been written to anticipate the addition of CSS3-::outside and ::inside generated
// content (and perhaps XBL).  That's why it uses the render tree and not the DOM tree.
static RenderObject* hoverAncestor(RenderObject* obj)
{
    return (!obj->isInline() && obj->continuation()) ? obj->continuation() : obj->parent();
}

static RenderObject* commonAncestor(RenderObject* obj1, RenderObject* obj2)
{
    if (!obj1 || !obj2)
        return 0;

    for (RenderObject* currObj1 = obj1; currObj1; currObj1 = hoverAncestor(currObj1))
        for (RenderObject* currObj2 = obj2; currObj2; currObj2 = hoverAncestor(currObj2))
            if (currObj1 == currObj2)
                return currObj1;

    return 0;
}

void RenderLayer::updateHoverActiveState(RenderObject::NodeInfo& info)
{
    // We don't update :hover/:active state when the info is marked as readonly.
    if (info.readonly())
        return;

    DocumentImpl* doc = renderer()->document();
    if (!doc) return;

    NodeImpl* activeNode = doc->activeNode();
    if (activeNode && !info.active()) {
        // We are clearing the :active chain because the mouse has been released.
        for (RenderObject* curr = activeNode->renderer(); curr; curr = curr->parent()) {
            if (curr->element() && !curr->isText())
                curr->element()->setInActiveChain(false);
        }
        doc->setActiveNode(0);
    } else {
        NodeImpl* newActiveNode = info.innerNode();
        if (!activeNode && newActiveNode && info.active()) {
            // We are setting the :active chain and freezing it. If future moves happen, they
            // will need to reference this chain.
            for (RenderObject* curr = newActiveNode->renderer(); curr; curr = curr->parent()) {